Lefsky: I went to the University of Virginia to study the modeling of forest structure. My graduate advisor was working with NASA, and one day he came back with a single waveform lidar graph, one of the first ever produced. That was it: I knew this was what I wanted to work on.

What on Earth: What do you mean by forest structure and why go to the trouble of studying it?

Lefsky: We were looking at things like the size and number of stems in forests. We were also looking at how forests change over time and across landscapes. It’s critical to understand forest structure if you want to understand how much carbon forests are storing. You need to know whether a forest is growing, in stasis, or has been disturbed. We used to study this kind of thing by basically counting stems. But when I looked at that waveform lidar data, I could see it was a record of exactly the same thing, but from a completely different perspective.

What on Earth: I’m guessing you could collect in seconds the same amount of data it takes weeks to get in the field?

Lefsky: Actually, less than a second.

What on Earth: But are there insights that you can get from the ground that you can’t get from space?

Lefsky: Sure, but you have to keep the scale in mind. In the field, we basically estimate forest height by measuring diameter of trunks at breast height. That’s sort of like trying to study a person’s size and metabolism by measuring the diameter of their ankles. Lidar gives you a whole bunch of new information about the vertical structure of forest canopy. This is something that’s hardly ever investigated from the ground, or could only be investigated with great difficulty.

What on Earth: What are the most satisfying and frustrating aspects of working with remote sensing data?

Lefsky: I love what I do. I am incredibly lucky. I don’t really see frustrations, just challenges. In this case, there are enormous challenges involved with working on a completely new kind of data and figuring out how to process such large amounts of information. The flip side is that coming to new levels of understanding about what’s going on in the world is incredibly satisfying.

What on Earth: If there was one thing you wish people knew about your science, what would it be?

The U.S. Coast Guard Cutter Healy, our chunky red-and-white icebreaker, sits at the gates of the Arctic Ocean. In the wee hours this morning, the sun set and quickly rose again, and a rainbow stretched up into low clouds. The ICESCAPE mission had reached station 5 of a seven-stop transect of the Bering Strait, between Fairway Rock — resembling Kong Island, but with pointy ears — and Little Diomede (U.S.) — something like the “Cliffs of Insanity” in The Princess Bride. Close by is Big Diomede (Russia), topped with fog.

Movie references aside, this is a dramatic spot in which to find yourself when you wake up in the morning — or in the evening, as is the case for the half of the science crew working the night shift to process the samples.

It seems that no matter how many times a scientist has been to sea, it doesn’t get old. Greg Mitchell (below right), a specialist in ocean optics from the Scripps Institution of Oceanography, reckons he has spent about four years of his life aboard ships. His first trip to the Arctic was in 1987, his first year at Scripps. Mitchell’s research has taken him all over the world — to Antarctica and back again many times — but he hasn’t been inside the Arctic Circle since 1989. He expects change.

Observing the system…..and how it interacts with the edge of the sea ice…..and what’s going on with the ice melt…..and how it affects the ocean…..those principles won’t be any different than they were 20 years ago. “What we’re clearly seeing is that the sea ice is reducing more and more all the time,” said Mitchell. “This means less sunshine reflecting off the ice back into space, and more getting into the ocean.”

He expects the increase in sun-light on the sea to do three things:

“The light that’s not reflected will heat the ocean, accelerating the warming and accelerating the melting of the sea ice.”

“As the ocean warms it becomes more stratified. If you dive in a lake in the summertime, it’s warmer at the surface. But as you dive down, you feel the cold. That’s because the warm water is lighter than the cold water, and it stays at the surface. That’s thermal stratification. As you warm the ocean, it’ll stratify more and that will create a warm layer with a lot of light for algae to bloom (as long as they have nutrients).”

“More light in the ocean should cause more total photosynthesis in the Arctic, so we’ll lose habitat for polar bears but we’ll gain habitat for plankton.”

Like the rest of us, Mitchell is concerned about that. “I’m not saying it’s a good trade off. I think we should leave things alone. But the system’s changing, and as it changes we don’t know what the consequences of those changes will be. It’s hard to say what we could do. What we really need to do is to find a way for humans to have smaller footprint on earth. So we need to understand the processes better and then we need to model it.”

That’s why he’s here.

Mitchell, along with his group from Scripps, is involved in ground-truthing the optical properties of the Arctic Ocean (photos at the top and bottom of this post). That is, he’s helping to ensure that what they see at the surface squares up with the methods NASA satellites use to assess ocean color, an indicator of the level of chlorophyll and, by proxy, phytoplankton. NASA’s satellites measure the color of the ocean by flying over the earth and picking up blue, blue green, and green. If there’s not a lot of algae, the ocean is blue. If there is a lot of algae, the ocean is green.

But color is just one way of looking at phytoplankton levels. In order to truly assess the situation — for example how much carbon dioxide the phytoplankton are taking in – scientists need to assess the processes at work in the sea. “The optics don’t tell us this, so we have to take water samples, process the water, and then relate that to the optics we measure from the ship,” Mitchell said.

The global mapping you can see on the NASA site uses mathematical equations developed from the shipboard work. Satellite validation and calibration is based on the findings of scientists who go to sea and study the water to see what’s living there. Mitchell’s research group claims responsibility for about 20 percent of the global observations used by NASA for their models to convert satellite-measured optical measurements to chlorophyll estimates.

The data contributes to models that allow prediction of primary production — the growth and health of organisms — under various conditions. Mitchell’s instruments include a small optical profiler — a fish-shaped instrument lowered from the Healy’s bow — and an optical package of instruments that measure water properties when it is lowered from the powerful A-frame at the stern.

“As ecologists, we don’t want to just know what color the ocean is,” he said. “We want to know how much plankton there is.” He walks to the edge of the ship and looks over the rail. “Now what we’re seeing out here is green water. There’s a lot of chlorophyll.” That means a strong pulse of phytoplankton, busy photosynthesizing the extra sunlight.

There’s a sign on the door of the room I share with Sharmila Pal and Emily Peacock. It’s a green square of plastic engraved with a picture of a polar bear and the words “SCIENCE – LATE SLEEPER.” So many of the scientists aboard Coast Guard Cutter Healy for the ICESCAPE mission are awake through the night that the ship’s engraver, Chief Warrant Officer 3 Sean Lyons, has turned out a special edition of late sleeper signs, complete with a rocket ship for NASA. Almost every door boasts a sleeper sign of one kind or another.

The reason? Aboard ICESCAPE, the science goes on 24 hours a day. We’re on a path to the far north, steaming from station to station through the night. Sometimes we’re in ice, sometimes we’re in open ocean, sometimes there’s a mix. Sometimes, there are walruses and seals. Each group of scientists has divided their schedule into shifts, so while some are catching their zzz’s behind those “late sleeper” signs, others are awake and overseeing operations, making measurements, and processing samples.

NASA’s Stanford Hooker takes the small boat out to measure light and take water samples, away from the interference of the ship. Karen Frey’s group from Clark University works on ice stations and takes Van Veen grabs in the open sea. (It’s like a giant pooper-scooper that scoops sediment from the ocean floor).

Bob Pickart of the Woods Hole Oceanographic Institution works to assess currents and other elements of physical oceanography, such as eddies and upwelling, as we pass through the ocean. James Swift, from Scripps Institution of Oceanography, oversees the CTD, a rosette of siphons and bottles triggered to sample water at various depths. (CTD stands for conductivity, temperature, and depth.) Greg Mitchell, Rick Reynolds, and their groups from Scripps measure the ocean’s optical properties with a small profiler dropped from the bow and with the Inherent Optical Properties (IOP) package of instruments deployed from the stern.

Sketch by Karen Romano Young

“We’re all working on different pieces of the same puzzle,” Reynolds says. “It’s impossible for one group to measure all we need to know. [Chief Scientist] Kevin Arrigo’s group is looking at core pigments, the plant pigments in the water column. Others are looking at chemical analyses of the nutrients in the water. It’s a big team effort. The ice people are working in a completely different environment, but there are algae in both places.”

The $250,000 IOP suite of instruments assesses the health of the ocean by analyzing the absorption and scattering of light by particles suspended in the water, including chlorophyll-rich algae; the quantity and quality of algae (the health and growth rate); and the presence of minerals and sediment. Each instrument on the IOP contributes to a picture of the makeup of the particles by assessing changes in light transmission.

“We start at the top,” says Reynolds (shown at left). “We look at what the NASAsatellite sees — the sea color — and parse out the differentcharacteristics of the water — how much algae, and what else is there,such as minerals from rivers, re-suspended sediment (mud stirred intothe water) and melting ice.” The resulting data will help thescientists develop new algorithms — equations for solving problems –to support the satellites.

NASA ice- and ocean-observing satellites, now working for more than ten years, are beginning to allow us to examine changes in the climate. One purpose of ICESCAPE is to look at the ocean with greater detail than the satellites offer, in order to improve and refine the interpretation of the satellite data.

“We’re here because NASA wants to know what the satellites are seeing right here at the stations,” says Reynolds, “where nobody else may sample for decades, because the ocean is so vast.”

The hypothesis has been proved conclusively aboard the Coast Guard Cutter Healy: I can officially sleep through anything. Yesterday [June 26] we hit what chief scientist Kevin Arrigo calls the heavy ice, northwest of Point Barrow, the northernmost point in the United States. Almost immediately we spotted a polar (right) bear, but haven’t seen one since. You can’t blame them for staying away from the Healy as it slams its 16,000 tons — plus the combined weight of everyone who spent the day eating the chocolate croissants Emily Peacock baked — into the ice.

Early this morning, the ice scientists stood on the bridge and targeted a floe for an “ice station.” For nine hours, we tried to get to it. Slowly and steadily, the ship made a path, ramming, cracking, or backing and ramming again, and the chopped-up ice in our wake soon froze together behind us. Scientist Sam Laney wishes he had a computer application that would detect seismic disturbances, saying he has lived through earthquakes registering 5.5 on the Richter scale and the vibrations didn’t feel as strong as they do right now.

[Laney commented later: “I actually downloaded a program last night and took a few hours of measurements in the aft hose reel room. I am not a seismologist, of course, but I’m estimating between 4.3 and 4.9 on the Richter scale based on these crude measurements.” This is why I like to hang out with scientists. ]

You can see the ice on a map compiled from satellite data, but the reality of the sea ice is right here at sea level. It’s quite different thing to see it in a satellite image as opposed to falling over in the shower because your ship is tilting as it climbs a ridge of jammed-together ice floes and slides back down.

The sea ice measurements made by a dozen scientists on the ice for our station will help confirm details in the satellite maps, just as the work of those studying optics in the open sea will add to the sea color (chlorophyll) mapping that NASA does.

But there is an additional method of observing the Arctic Ocean that I’d like to tell you about because it has been so exciting to everyone here at ICESCAPE. You don’t have to interpret maps or charts of data. You just have to sit back, put your feet up, and check out Sam Laney’s pictures.

Sam’s images come from a stream of water coming up through a hose at Healy’s stern. All the microscopic organisms in the stream parade in front of a camera, sitting briefly for a snapshot before returning to the sea. The instrument, which is set up deep below in the aft hose reel room, is called the Imaging FlowCytobot (below right). It was developed at the Woods Hole Oceanographic Institution.

Flow cytometry has long been used in medicine for counting cells — such as platelets – in blood samples as they are squirted past a laser. Oceanographers use flow cytometers to count the small cells that live in seawater, such as phytoplankton (photosynthetic microbes) and other small organisms.

Imaging flow cytometry takes this approach one step further by triggering a camera every time a cell passes in front of the laser beam. Software on the imager immediately crops out the background from the picture to focus on the critter that was just photo-graphed. The revolutionary result is a steady flow of pictures of organisms as small as 2 microns living in seawater. It looks like a case of jewels: individual round-bodied gems, bigger broach-like diatoms chains (above right), and monster-like ciliates that prey on the smaller critters.

In the past, scientists were able to gather steady flows of water and videotape the plankton at magnification. But managing this huge amount of data would have taken such incredible man-hours that it was impractical for use at sea. The Imaging FlowCytobot does it for us, snapping off a continuous stream of pictures — as many as ten thou-sand cells in a volume of seawater no bigger than a AA battery

Laney’s sea-going imager is an outgrowth of an underwater Imaging FlowCytobot that his collaborators Heidi Sosik and Rob Olson have operated for several years at the Martha’ Vineyard Coastal Observatory off Massachusetts. ICESCAPE is the first time the instrument has been used at sea to survey broad regions of the ocean.

“We are seeing what’s in the water immediately, not after the fact in a lab,” Laney explained, “so it’s obvious when the water — and what’s in it — changes. In the images taken north of Dutch Harbor, there weren’t many cells out there because it’s the open ocean. But in the Bering Strait, the jewels were much more elaborate because we were closer to shore. A large diatom chain indicates an ecosystem that has a lot of nutrients and is highly productive.”

Laney, Sosik, and Olson hope to see Imaging FlowCytobots placed aboard long-term, deep-ocean moorings in the open sea, such as those that will be deployed as part of the Ocean Observing System.

Of course, some of the fun is just seeing the plankton in action. Sometimes you can simply tell that they’re ailing or dying. In one memorable stretch of sea, off Point Lay, the Cytobot caught a stream of diatoms in the act of dividing and reproducing. Then there are the horror shots, in which a ciliate stretches its cilia toward a hapless phytoplankton.

What do NASA techies do with their spare time? They make rock-n-roll videos. Not the big-hair, booty-shaking, smoke-and-fire kind. They help make rock videos that would make their daytime colleagues proud or jealous, or both.

The rock band OK Go prides itself on creative visual expressions of their music, and they wanted an extra dose of gee-whiz fun for their song “This Too Shall Pass.” In early 2010, the group enlisted the help of Syyn Labs — a self-described “group of creative engineers who twist together art and technology.” The Syyn Labs fraternity included (or ensnared) four staff members from NASA’s Jet Propulsion Laboratory.

[Remember to turn your sound on.]

OK Go requested a Rube Goldberg machine as the centerpiece of a video. To borrow from wikipedia, a “Rube Goldberg machine is a deliberately over-engineered machine that performs a very simple task in a very complex fashion, usually including a chain reaction. The name is drawn from American cartoonist and inventor Rube Goldberg.” Think of the classic board game Mousetrap or your favorite chain reactions from Tom & Jerry cartoons.

More than 40 engineers, techies, artists, and circus types spent several months designing, building, rebuilding, and re-setting a machine that took up two floors of a Los Angeles warehouse. The volunteers went to work after work, giving up many nights, weekends, and even some vacation days to build a machine that has drawn more than 13 million views on YouTube.

What on Earth caught up with these rock-n-roll moonlighters to learn more about the machine and video.

What on Earth: What was your role in the creation of the machine, and what was the inspiration behind your piece?

Eldar: My main role was to help design and construct the descent stage (2:06 to 2:28 in the video). The inspiration for the rover was a small Japanese Rube Goldberg machine that had a tiny mock-up of a mouse rover, about the size of a Hot Wheels car. It struck me that since I am representing JPL, we should have a Mars Rover in our machine.

Chris: I helped finish up the sequence of interactions and the filming. I have a couple things that I was involved with, but cannot take complete ownership of any. But during the filming, I redesigned the beginning dominos (0:06-0:18 sec.) and helped set them up between the numerous takes (60+).

Mike: I worked on the tire ramp, mostly focusing on wiring the relay circuits for the lamps that were triggered by the tire. You’ve got to wonder when a mechanical guy does electrical work. A friend from CalTech told me about a band making a music video featuring a Rube-Goldberg machine. Any time I’ve seen one in a movie, like in Pee Wee Herman’s Big Adventure or Chitty Chitty Bang Bang, I’ve always wanted to make one myself.

Heather: I helped make sure all the modules came together in the first half of the video. I also worked on the intro, the Lego table, and the inflatables. There were a few guiding principles behind the machine. No magic: Mechanisms should be understandable and built from found objects where possible. Small to big: The size of the modules and parts becomes bigger over the course of the video. One take: As in their other videos, the band wanted the entire piece shot in one piece by a single handheld camera.

What on Earth: How many “takes” did it take to get the machine to work?

Mike: Before filming, it took more tries to get things right than anyone could ever have counted. Sometimes I’d spend three or four hours just fiddling with one part to get it right. Even then, it often got changed a couple days later to something else.

Heather: We learned something very important about physics in the process of making this video. It is much harder to make small things reliable. Temperature, friction, even dust all greatly effect the repeatability and timing of the small stuff. The first minute of the video failed at a rate that was tenfold of the rest of the machine. Remembering that rule about getting everything in one shot — if your module is further down the line in the video, you’re in big trouble if it doesn’t work! The machine took half an hour and 20 people to reset.

What on Earth: What’s the funniest or strangest thing that happened on the set?

Chris: Realizing that a number of PhDs built one thing and a clown from a circus built another part. There was no hierarchy. Everyone was there for the same purpose: to build a machine that worked and was fun!

Mike: I helped assemble the sequence between the piano and the shopping cart (1:34 to 1:41). The tetherball pole was supposed to trigger the shopping cart, but when we played the song, the timing was off. The band wanted more delay so that the cart crashed at the end of ‘when the morning comes.’ I added in a sequence using a director’s chair, a piano cover, a waffle iron, and a 10-pound weight to give the necessary delay. Heather’s shoe became part of the sequence, too.

The director’s chair has a rope holding one arm in place. My first thought on holding this rope was to use an umbrella, but Heather told me there were already too many umbrellas in the machine. I rummaged around the warehouse and found a high-heeled shoe sitting around a bunch of junk, and I thought this would make a great holder for the rope. I fastened the shoe to a 2-by-4 with three large wood screws, pried off the rubber tip of the heel, and sanded it a bit to allow the rope to slip off with just the right amount of force.

Then Heather walks up with a friend, who says: ‘Heather, isn’t that your shoe?’ I thought she was kidding, but then Heather said, ‘What are you doing with my shoe?’ I still thought they were making a joke, but then I could tell that Heather was serious and getting mad. Then she started laughing and said: “The machine needs a high-heeled shoe!”

What on Earth: What is your favorite part of the machine?

Eldar: I think the beginning, where the ball bearing jumps out of the speaker when the music begins (0:24) is absolute genius. But the guitar hitting the glasses and taking over the music (1:24) is also quite phenomenal in timing and execution. There were so many things in this machine that blew my mind.

Heather: There are various ‘Easter eggs’ from the band’s other videos that are nestled within the machine. The most obvious is the treadmill video playing on the TV that gets smashed (2:37). But there are also references to the Notre Dame marching band video on the Lego table (1:17) — from the tall Lego drummer to the dancing grass people (I made those!).

Chris: My favorite is the falling piano! That thing took such a beating and was screwed together take after take. It only lasts for a fraction of the video, but it has such comical importance and was triggered after one of the best parts of the video — the clinking glasses.

What on Earth: So if you could quit the day job and get paid for such things, would you?

Mike: I don’t think so because I really like my day job. And even though working on the video was great fun, if it became a full-time job, I don’t think it would seem as fun anymore. The build seemed like a college frat house at times, and that would definitely go away if it became a job.

Eldar: No, I work on missions to other planets! This was fun, but the real deal is at NASA. They say that there is no business like show business. They can keep it.

Postscript: If you want to enter the world of music videos – or of the NASA engineer – you can make your own Rube Goldberg machine for the band’s video contest.

The newest bird in NASA’s flock — the unmanned Global Hawk — took off at 7 a.m. Pacific time today (April 2) from Dryden Flight Research Center at Edwards Air Force Base in California. The flight is the first airborne checkout of the plane since it was loaded with 11 science instruments for the Global Hawk Pacific (GloPac) mission.

Pilots are also streamlining processes to coordinate the workload while the nearly autonomous plane is flying at altitudes above 60,000 feet (almost twice as high as a commercial airliner). Operators and mission researchers are using the day to make sure all instruments are operating properly while in flight — particularly at the cold temperatures of high altitude — and communicating clearly with the plane and ground controllers. Mission participants expect to begin collecting data when actual GloPac science flights begin over the Pacific Ocean later this month.

GloPac is the Global Hawk’s first scientific mission. Instruments will sample the chemical composition of air in Earth’s two lowest atmospheric layers — the stratosphere and troposphere — and profile the dynamics and meteorology of both. They also will observe the distribution of clouds and aerosol particles. The instruments are operated by scientists and technicians from seven science institutions and are funded by NASA and the National Oceanic and Atmospheric Administration (NOAA).

…There is an old Latin quote: “Maxima omnium virtutum est patientia.” Or “patience is the greatest virtue.” When it comes to mounting science instruments on an aircraft, you need to continually return to that quote…

…During the integration this week, we’ve had to cut holes into the aircraft. I told Chris Naftel, the Global Hawk project manager, that we had to cut some holes into the plane for the Meteorological Measurement System. Chris replied: “I don’t want to hear anything about the holes. It pains me!” In spite of Chris’ pain, the little holes are critical for measuring winds. You’re now asking, what? Little holes? For winds? It’s actually a very slick little measurement that relies on the work of Daniel Bernoulli, a Dutch mathematician who lived in the 1700s…

Even though it’s sometimes convenient to think of the ocean as a great big bathtub, where turning on the tap at one end raises the water level in the whole tub, real sea level rise doesn’t quite happen that way. To understand why, you first have to realize that ‘sea level’ isn’t really level at all.

There are lots of reasons why the oceans are not level. For example, vast ocean currents like the Gulf Stream in the Atlantic Ocean and the Kuroshio in the Pacific actually reshape the ocean surface, causing it to tilt. As the planet heats up, changes in the prevailing winds (which drive most of these ocean currents) cause changes in the currents, reshaping our ocean and changing local sea level as a result.

Just as global warming does not raise land temperatures evenly, global ocean warming is not the same everywhere around the globe. Some regions of the oceans are heating up faster than others, and because warm water takes up more space than cold water, those regions experience faster sea level rise.

Finally, the water locked away in the great ice sheets of Greenland and Antarctica also shapes the ocean surface. As the ice sheets melt and lose water to the oceans, our entire planet feels the effects. The movement of mass from the ice sheets to the oceans very slightly shifts the direction of Earth’s rotation. This, along with changes in the gravitational pull of the ice sheets on the oceans, will reshape sea levels further still…

Oceanographer Josh Willis of NASA’s Jet Propulsion Laboratory was recently honored by the White House as a recipient of the Presidential Early Career Award for Scientists and Engineers (PECASE). Willis studies the ocean — particularly the height of the sea surface — with satellite data, though he also works with colleagues who put instruments below the surface of the water. By blending such measurements, he has already made a scientific mark in the study of sea level rise. We caught up with Josh — shown below with White House science advisor John Holdren and NASA deputy administrator Lori Garver — to discuss his inspiration, the importance of the ocean, and the necessity of communicating science.

WhatOnEarth: When you were a child, what did you want to be when you grew up? When did you decide you wanted to be an ocean scientist?

Josh Willis: When I was 9 or 10, I found a book about Einstein’s Theory of Relativity that my parents had lying around the house. I remember reading it and then peppering my parents with questions they couldn’t answer. (This was long before Google, mind you.) So for a long time, I wanted to be a physicist. A couple years of graduate school in physics convinced me otherwise, and I started studying oceanography at the Scripps Institution of Oceanography. Studying the ocean and climate appealed to me because I got to use all the physics and math I learned, but it was also closer to home and of practical importance to a lot of people. Plus, it’s just fun to say “oceanographer” whenever people ask me what I do.

WhatOnEarth: What is the best scientific paper you have written?

Willis: It’s tough to say. Sometimes the papers I think are important are different from the ones that other scientists remember best. But my papers on the causes of sea level rise — based on comparisons between satellite altimeter data, observations of ocean temperature changes, and changes in ocean mass measured by the GRACE satellite — were interesting and fun to write.

WhatOnEarth: What is the most important thing that few people know about the ocean?

Willis: The ocean is the silent martyr of global warming. We always think of global climate change in terms of the warming atmosphere, but it is actually the ocean that absorbs almost all of the extra heat and a whole lot of CO2. The warming contributes to sea level rise and changes ocean ecosystems, while the extra CO2 makes the ocean more acidic, threatening plankton and other tiny critters that make up the foundation of the oceanic food chain.

WhatOnEarth: Why do you feel compelled to talk to the public about your science?

Willis: Communicating our work is a really important part of doing science that most scientists sort of neglect. Figuring out new things about the world around us is only helpful if we communicate them to everyday people. Plus it’s fun and exciting to talk to non-scientists because the questions are often fun and interesting, and I come away feeling inspired and invigorated.

WhatOnEarth: What is the funniest or strangest question you’ve ever gotten?

Willis: I often get a chuckle out of the people who say that global warming is a vast conspiracy among scientists. Scientists love to prove each other wrong, and most of the time we can barely agree on simple questions like “why is the sky blue,” much less orchestrate a conspiracy.

WhatOnEarth: Is the PECASE award an affirmation or an inspiration for your career?

Willis: This is definitely a great honor and inspiration. When President Obama met with us, one of the first things he told us was how nice it was to honor a group of scientists still in the early stages of our careers. “All of you folks are younger than me!” he said. But he also made it clear that he expected a lot from us in the future. That’s a pretty big inspiration when the President tells you he’s expecting great things. And it’s a pretty big responsibility, too. I guess that means it’s probably time to get back to work now…

The Earth is a bit like the human body; its temperature is very finely balanced, and when it gets slightly out of whack, big things can happen. In the case of our home planet, gases in the atmosphere play a vital role in maintaining this delicate equilibrium, by balancing the absorption and emission of all the electromagnetic radiation (microwaves, infrared waves, ultraviolet light and visible light, for example) reaching the surface of the Earth.

As reported recently, the Earth is getting warmer. Scientists believe the main driver behind this warming trend is rising levels of man-made greenhouse gases. These gases, which we pump out into the air, act to trap heat radiation near the surface of the Earth that would otherwise be sent back out into space. Carbon dioxide (CO2) is the Paris Hilton of greenhouse gases, and gets a lot of face time because its concentration in the atmosphere has increased relatively rapidly since the Industrial Revolution. But methane, nitrous oxide, hydrofluorocarbons (HFCs), chlorofluorocarbons (CFCs) and perfluorocarbons (PFCs) are also important agents of global warming. Some of them are actually much more potent than CO2 and they stick around for hundreds to thousands of years longer. This has some scientists concerned that these B-listers could actually impact global temperatures significantly more than CO2.

In a new paper, Partha Bera and colleagues at NASA’s Ames Research Center and Purdue University put these gases under the microscope to find out exactly why they are such powerful heat trappers. They focus on CFCs, HFCs and PFCs — all chemicals containing fluorine or chlorine — that are used in medicine, fridges, and as solvents, among other things. By probing the molecular structure of these compounds, they have found that molecules containing several fluorine atoms are especially strong greenhouse gases, for two reasons. First, unlike many other atmospheric molecules, they can absorb radiation that makes it through our atmosphere from space. Second, they absorb the radiation (and trap the heat) very efficiently, because of the nature of the fluorine bonds inside them. (In technical terms, fluorine atoms create a larger separation of electric charge within the molecule, and this helps the molecular bonds absorb electromagnetic radiation more effectively.) HFCs and other fluorine-based gases have been called “the worst greenhouse gases you’ve never heard of.” Now we know why.

Until now, scientists had not looked in detail at the underlying physical or chemical causes that make some molecules better global warmers than others. Bera and colleagues say that their work should help improve our “understanding [of] the physical characteristics of greenhouse gases, and specifically what makes an efficient greenhouse gas on a molecular level.” They hope their findings will be used by industry to develop more environmentally-friendly materials.

In one hallway of this meeting, someone will tell you about the atomic properties of rocks; around the corner, someone will explain the motion of entire continents. You can walk into a room and learn how the solar system began, then into another to hear about how it might end. It reminds me of Robert Frost: “Some say the world will end in fire, some say in ice…”

For those of us who love earth science, the AGU meeting is a smorgasbord, and I have been bellying up to the buffet since 1995. The menu this year includes more than 15,516 choices — scientific posters, lectures, and presentations — spread over five days.

The AGU is one of the weeks when I most love my job. I get to learn what will be in tomorrow’s textbooks, museums, and classrooms, and observe science history as it is being written. Which findings will hold up and which will be rejected? It’s a privilege to be around for the debate.